Lithography performance of contact holes: I. Optimization of pattern fidelity using MPG and MPG-II

Proximity effects make optimizing the pattern fidelity of contact holes one of the most challenging lithographic tasks in maskmaking. This paper examines the exposure and process parameters that influence the pattern fidelity of contact holes on a photomask from both a modeling and an experimental approach. To optimize contact critical dimension (CD) uniformity and corner rounding, a range of exposure and process variables is examined. These variables include MEBES writing strategy, input address, spot size, development time, and data bias. ProBEAM/3D, an electron- beam modeling software program, is used to model contact hole performance, and the results are verified with a design of experiments protocol using the same variables as in the simulation study. A simultaneous optimization of these parameters is instructive in matching the appropriate writing strategy and technology node with the desired quality of the contact hole.